1. Field of the Invention
The present invention relates to a wireless communication system and a wireless communication terminal, and more particularly to a wireless communication system capable of changing dynamically a charge rate and a wireless communication unit which can be used in the wireless communication system.
2. Related Background Art
Conventional cellular wireless communication systems for public use, relying on a micro cell or the like, including PDC (Personal Digital Cellular), PHS (Personal Handyphone System), and GSM (Global System for Mobile communications), make use of, as a parameter for changing the communication fee (charge rate), static information such as a charge condition (service plan) agree upon when the user of a wireless communication terminal subscribes the service provided by a carrier, or communication time.
Accordingly, such wireless communication systems do not use dynamic information (a communication traffic volume or a remaining wireless resource amount) as a parameter for changing a charge rate, so that it is not possible to charge minutely depending on a situation for each wireless cell at the place or time where communication occurs.
In Japanese Patent Application Laid-Open No. 5-183495, it is disclosed that in order to make effective use of wireless resources within a wireless communication system, a new call is limited by setting the service charge for a newly arising call to be higher than the ordinary fee, if the traffic volume of service channel in a wireless base station has exceeded a predetermined value. Also, in Japanese Patent Application Laid-Open No. 5-183495, it is disclosed that the fee information notified from a wireless base station is output by voice or images at a mobile station such as a portable telephone, so that the user can determine whether to make a call or not.
Further, in European Patent EP0597638A1, it is disclosed that the charge rate is changed in accordance with the volume of service channel in a wireless bass station, and the user can make a call after confirming the charge rate for use.
However, in Japanese Patent Application Laid-Open No. 5-183495 and EP 0597638A1, there is no consideration about how to notify the fee information from a wireless base station to a mobile station.
Also, in U.S. Pat. No. 5,303,297 (Japanese Patent Application Laid-Open No. 5-199331), it is disclosed that on a call request, a charge rate is determined by calculating the utilization factor for all the available resources in both wired section and wireless section which are usable for a communication between a calling terminal and a called terminal, and is notified to the calling terminal.
However, with a method of determining the charge rate in accordance with the amount of service resources including the wired section, as in U.S. Pat. No. 5,303,297 (Japanese Patent Application Laid-Open No. 5-199331), there is the problem that the calculation of charge rate is complicated, and it takes longer time to calculate the charge rate. To calculate the charge rate, the service situation for all the paths from the calling terminal to the called terminal must be examined, and traffic is further increased to communicate the information as to the service situation. Also, load on the system would be increased.
In the conventional examples as described above, when the charge rate is changed dynamically in accordance with the amount of service resources for the wireless base station or the whole system, no consideration is taken as to how to notify the charge rate.
Also, in the conventional examples, no consideration is taken as to how to change the charge rate to be optimal for the user.
Further, usability of the terminal in the system in which the charge rate is dynamically changed is not considered.